Performance Evaluation of Synthetic and Natural- Based Surfactants for Chemical Enhanced Oil Recovery

Contemporary studies have demonstrated the ability of some natural materials to recover oil thereby replacing synthetic materials; however, the effectiveness of these natural materials in recovering oil at high temperatures, pressures and in hard waters needs to be determined. The research aims at comparing the recoverability of a natural and synthetic surfactant with divalent ions being present and under reservoir conditions after which a cost analysis at field scale is conducted. Two surfactants namely, Hibiscus calyx extract and sodium dodecyl sulphate (SDS) were assessed in the laboratory using hard brine. Phase behaviour and sandstone core analysis was conducted to ascertain the effectiveness of these surfactants in recovering residual oil at high temperature and pressure of 80˚C and 8000 psi respectively. Upscaling from laboratory to field scale and a comparative cost analysis was performed. Results showed a high compatibility of both surfactants in hard brine with an absence of Type III micro emulsion. At reservoir conditions, Hibiscus calyx extract resulted in an increased oil displacement efficiency and additional recovery of88% and 24% than SDS which resulted in a displacement efficiency and additional recovery of 72% and 19% respectively. Using an upscaling factor to field scale, a chemical injection rate of about 5 barrels/day was attained. Comparative cost analysis showed that the natural surfactant is more cost-effective. This study proposes the use of natural surfactants in harsh oilfield conditions, eliminating processes of brine softening with economic advantages of reusing produced water to prepare chemical slugs for EOR treatments.